Starcraft AI blog

Today’s game Randomhammer vs Flash is unbelievable. What I mean is, if I didn’t know that the replay was generated automatically by bots playing, I would assume that it was a setup. That should not happen!

Randomhammer rolled protoss and opened with 1 gate and dragoons. Flash put down 2 gates and made zealots, so of course Flash had more units. Randomhammer had an easy defense in principle: Make a fighting withdrawal with the dragoons, to buy time and to put some bruises on the zealots. When and if the zealots reach its base, Randomhammer should have enough dragoons to outmicro the zealots, and it can run probes if necessary.

Randomhammer has no understanding of any of that. The only withdrawal it knows is headlong retreat, and instead of running probes it fought with them. When the surviving zealots were finally driven off, only 2 probes survived. Furthermore, the 2 probes were collecting gas and had no ability to switch to mining minerals, so Randomhammer had zero income for the rest of the game. “Game over,” I thought. It was 6 Randomhammer dragoons, versus an opponent that was briefly behind in units, but now had its own dragoons and 2 running bases.

As I expected, Flash soon rivaled Randomhammer’s army size. But I could hardly trust my eyes when I saw the fight. Flash had just started dragoon range, and could not cope without it! The 5 ranged dragoons (1 froze in the middle of the map) outmicroed Flash’s dragoons and remaining zealots by an extreme margin, with Flash rarely getting shots off. Randomhammer smacked down the army and a long stream of reinforcements which came in piecemeal.

Then Flash showed that it is every bit as careless with probes as Randomhammer, and instead of mining safely in the main and building up a ramp defense force while the natural was slowly flattened, kept transferring probes. Randomhammer finished the game with 4 dragoons, having lost only 2 against a much larger number of enemies. Not plausible, only true.

The next Steamhammer version will turn off gas collection for terran and protoss when there is reason to, as it always has for zerg. It’s a simple feature, and I think it will make a difference.

Next: The theoretical right way to analyze the enemy’s build.

A funny game, a comedy of errors: Steamhammer versus Tyr terran by Simon Prins, on the map Tau Cross. Steamhammer opened with 2 hatch mutalisks, and Tyr bunkered itself in and went with infantry on one base.

Phase 1: Steamhammer fiddled around with its mutalisk force, picking off several building SCVs but mostly wasting time.

Phase 2: Steamhammer happened to notice that the terran mineral line was also a possible target. “Oh, look, terran has SCVs mining. I didn’t know that!” Tyr didn’t defend but moved out to counter instead and lost all SCVs. Steamhammer had 3 mining bases to 0, and only had to survive Tyr’s attack to win. Terran could not reinforce, so that was easy, right?

Phase 3: Instead of defending itself, Steamhammer decided to sacrifice every mutalisk against the meaningless bunker. It also wasted units piecemeal against the terran ball. Tyr destroyed the zerg main and natural. Steamhammer lost many drones by sending them to mine gas at bases that were under attack. That makes 3 big mistakes, more than enough to lose.

Phase 4: Tyr spread out to find the zerg 3rd base, found it after a few tries, and then—decided to send its army home to rest. “No zerg anywhere! Not that I’ll admit, anyway.” The marines in the picture saw the base, and that is when Tyr started to send its troops home.

Phase 5: Steamhammer slowly recovered from 7 drones at its third base. It restarted its tech from zero, put down 4 sunkens because it knew there was a scary army out there, and belatedly switched to lurkers. Steamhammer made far too many drones before moving out, but finally sent a lurker and won easily because Tyr had no detection. The mutalisks had also killed the comsat.

In the picture, nothing can stop the lurker, and more lurkers will come. You can see in the minimap that Steamhammer has retaken its main and natural and a mineral only base as well.

Both sides showed a lack of resilience. This time, Tyr turned out to be lacking a little more. Besides its opportunity to attack and win, Tyr had an unfinished science facility that it could have canceled (it’s in the upper right of the last picture). Then it would have had the resources to make an SCV and get back to mining.

As its opponents have long since noticed, ForceBot has become a 5 pooler. It does an economic followup, so there is some interest.

The picture shows Oyvind Johannessen’s base from ForceBot versus Oyvind Johannessen. Random Oyvind Johannessen ended up zerg, and was ready for the rush. Unfortunately, the defending zerglings chose to follow a circling overlord, so Oyvind lost its opportunity to return the pressure.

ForceBot is trying to catch up in workers. As you can see in the minimap, it is 3 bases versus 2. Although it was ZvZ, neither side played aggressively, and the game went on for 45 minutes. It was fun, for a low-level bot game.

Oyvind barely defended itself while the zerglings were suffering from overlord fascination, and ForceBot started to dominate. ForceBot went hydra-lurker and took the map, rather a change from the 5 pool opener.

Oyvind understood how to hold on in a desperate situation. See all the blood? ForceBot could not coordinate an attack to climb the ramp. Oyvind is long-distance mining its natural and eventually retook it, while ForceBot went passive and sat around with its maxed army. The game ended when Oyvind mined out its natural and crashed. I expect that ForceBot would have won on points after the game time ran out.

This version of ForceBot seems to play similarly against all races: 5 pool, try to build an economy, lair, hydra-lurker. It’s quite different from the AIIDE 2017 ForceBot. It seems to have some added defensive smarts; it doesn’t appear to make pre-emptive sunkens willy-nilly any more, at least not often.

I’m still going through AIIDE 2017 games in which Steamhammer lost to weaker opponents. Steamhammer scored 98-12 against ICEbot. I thought this game on Tau Cross was full of depressing and/or informative mistakes.

The biggest mistake is that Steamhammer didn’t usually scout or react to enemy expansions. That is fixed in the development version. I think the new version would have won this game easily, despite the second mistake.

The second and interesting mistake came when ICEbot tried one of its 4 goliath drops.

Steamhammer’s notion of “this base is under attack” is not accurate. One goliath wandered outside Steamhammer’s danger recognition zone and found itself still in weapons range. It killed dozens of drones and eventually one of the hatcheries before dying. In the picture we see the totally non-dangerous goliath killing drones while Steamhammer does nothing because “the base is safe now.”

This weakness is not fixed. I’ve seen it before. The base defense code is inherited from UAlbertaBot and needs a bigger rewrite than I’ve given it.

ICEbot was playing weakly too, though, or else it would have scored more than 12 wins in 110 games. Zerg recovered from the huge deficit and made a fight of it. The game timed out after an hour with the map mined out and the winner still undecided. ICEbot was given the victory on points.

Steamhammer’s losses against ICEbot followed a curious pattern, by the way. Steamhammer lost in rounds 0, 2, 4, and 6. Then in the rest of the tournament, which ran to round 109, it lost 8 more games. Neither bot was learning, so the early losses of every second game were purely coincidence.

I thought this picture was funny. In a game yesterday against Iron, McRave fast expanded and walled off one of the bridges to its natural, but left the other bridge open. Vultures cannot pass the wall, but they happily took the other bridge and Iron won easily.

McRave seemed to mess up its build, getting dragoons too late. (The underlying mistake may have been taking gas at the natural instead of the main.) But the idea is sound. McRave is narrowing the entrance to its natural, making it easier to defend against vultures. A small number of dragoons can block a narrow entrance, either early in the game when there are only a few dragoons on the map, or later when the main army is away and the only dragoons around are those rallied from the gateways.

Its next game against Iron was on Roadrunner. McRave won using the same idea of narrowing the entrance.

McRave’s dragoons beat Iron, so they played well by bot standards. But I see room for improvement. Vultures can pass either left or right of the upper gateway. I think the first 2 dragoons should plug the gaps so that vultures are physically blocked. Iron will lay mines to force its way in, and then the dragoons can retreat to the defense line McRave actually held, the gap between the lower gateway and the nexus. The farther away the vultures and their mines are kept from the probes, the better.

I’ve been watching the replays of Steamhammer’s losses in AIIDE 2017 against its lowest-scoring opponents. I reason that if A beats B nearly every time, then a weakness which causes A to lose to B must be a severe weakness that I should fix.

Steamhammer scored 105-5 against Overkill in this tournament. The losses were all due to the same basic strategy blunder, teching too fast and not making enough mutalisks. One loss was an interesting one that taught me something: It involved making too many devourers.

Here’s the game. Steamhammer played its turtle opening, which it was set to do 1% of the time in ZvZ. (It’s a weak opening, but it is played rarely and it poses challenges that some bots can’t meet, so I don’t mind.) Meanwhile, Overkill also turtled, on 2 bases instead of 1 but with fewer drones.

As in the other losses, Steamhammer spent on zerglings and on teching to hive when it should have been making mutalisks. Overkill flew over, killed a lot of drones—then left for no apparent reason. Overkill was ahead, but Steamhammer could recover. Mistakes like that may explain how Overkill scored so poorly. Steamhammer still didn’t feel like making many mutas, but it did add scourge and morphed a greater spire, which (since it was behind and had already invested in a hive) was reasonable.

Steamhammer started morphing its mutas into devourers. It can’t catch up in mutalisks, so it was a good try to turn the game around. But as I watched, I realized there was a flaw in the strategy logic: It wanted to morph all the mutalisks and go straight devourer. The unit mix is declared as mutalisk + devourer, but because of how gas accounting works, the strategy boss preferred to turn gas-heavy mutas into mineral-heavy devourers.

Overkill finally moved out when it was maxed, with 72 mutalisks. Steamhammer had 20 devourers and 4 mutalisks, plus a fleet of scourge. Now, devourers are support units. They don’t do much damage; their benefit is that they splash acid spores which reduce the enemy’s attack rate and increase the damage taken, and to get the benefit you need fast-attacking units to deal the damage. Because acid spores only stack up to 9, it is not likely that 20 devourers will ever be useful, and definitely not if you fly them around in a group. I guess that about 6 devourers would have been best, certainly not more than 9.

The battle was hilarious. The devourers fought well enough, apparently not harmed by the known bugs, and instantly stacked their purple goop up to the limit of 9 on every Overkill mutalisk that appeared. Devourers are tough, and Overkill’s mutas had their attacks slowed, so the the devourers took a long time to die. But with only 4 mutalisks to deal damage, even though the damage per shot was 9+9 + 3+9 + 1+9 = 40 (spread over 3 enemies with mutalisk bounce) Overkill’s losses were minor.

The ultralisk cavern you can see in the picture was useless. Steamhammer never made an ultra. It shouldn’t have wanted to.

In the next version I’ve taken measures. Steamhammer tries to make more units, techs more moderately, and limits the number of devourers.

I thought these 2 games showed interesting mistakes.

Steamhammer-McRave

This game on Circuit Breaker was kind of disorganized on both sides, but fun. Steamhammer played its usual low econ zergling pressure, and McRave opened with cyber core before second gate, which was slow enough to give the pressure a chance. After a few tries, Steamhammer killed enough probes to make up for its own weak economy, and the game was on.

The fight went back and forth, the sides seeming about equal in economic growth, tech progress, and missteps. It was fun to watch.

Steamhammer: It’s only an overlord. No need to keep it safe. And that? Oh, it’s only another overlord.
McRave: Huh? Why wouldn’t I awkwardly split my army?

Then dark templar came out, and Steamhammer fell over. Zerg did not understand.

Steamhammer: What danger? I don’t see any protoss units that I can’t fight.
McRave: Exactly.

Steamhammer-KillAll

This game was a win but... ugh. Only because KillAll went above and beyond to play worse.

KillAll did its thing and sunkened up for safety. Steamhammer understands in outline how to win these games: Place zerglings in a containing position so the enemy can’t expand or attack, make drones while teching, then win with mutalisks. But (as against ZZZKBot in AIIDE) Steamhammer did not execute well. It placed the zerglings in a position that contained nothing, and in fact left the barn door wide open. Steamhammer even stepped back to let enemies pass, in reflexive fear of the distant sunkens.

Below you can see that Steamhammer is ahead in economy, tech, and army—yet Steamhammer is in trouble because its force is out of position, standing outside an enemy base that it cannot threaten while its own base is under attack. Meanwhile, KillAll decided that its attackers should focus down the lair to the exclusion of all other targets, so that Steamhammer’s drones were able to clear the zerglings with no losses.

I can’t say it’s an undeserved win. The winner made smaller mistakes. Only not small mistakes.

Next: Thoughts on the gas steal.

“Somebody” voted in a bunch of Steamhammer versus PurpleWave games. PurpleWave played different openings. Past versions of PurpleWave dominated Steamhammer with the forge-expand opening, taking advantage of Steamhammer’s mistaken macro decisions and weak scouting and tendency to collapse tactically in a big fight. But this PurpleWave has been losing some; it has new weaknesses. So the games are not the best, but they are still interesting.

Some of the games were proxy 2 gates. There were wins and losses, but I found those games not as interesting.

on La Mancha

This is the Steamhammer-PurpleWave game that Nepeta cast last Sunday, so I won’t go into detail. PurpleWave suffered bugs that caused it to warp buildings near the zerg forces and pull probes for no reason, so it did not develop its usual big advantage. What I find interesting about the game is the turning point, when zerg pulled decisively ahead: It was when protoss attacked the zerg natural and dealt great damage, destroying the drones.

The returning zerg army finally cleared the attack. The protoss army was trapped and could not retreat toward home. It should have “retreated” into the zerg main to try to deal more damage (and to pull the zerg army away from the front), but instead turned fatalistic and gave up without a fight. Meanwhile, zerg had many drones at other bases and quickly restored the losses, while the lost protoss army was not as easy to replace. The value of destroying drones depends not on the number of drones you kill, but on the number that survive somewhere....

on Icarus

This game was also a forge-expand, but the play was quite different. No obvious bugs bit. PurpleWave built 4 cannons, which is plenty for most circumstances... and Steamhammer busted them anyway.

Steamhammer killed probes too. Then I tore my hair out in frustration, because instead of pressing for the win, Steamhammer decided it was more important to simultaneously plant a spire, hatchery, evo chamber, and hydra den, and also grow its economy. Notice in the picture that, although Steamhammer has spent 4 drones on buildings, it is still ahead in workers—and PurpleWave has cautiously pulled probes for defense. The spire, by the way, was left unused until late. With 2 bases, PurpleWave eventually caught up from far behind and the game was on again.

Fortunes turned again, like last time, when PurpleWave overpressed and lost too much army at Steamhammer’s natural. Seconds after this picture, protoss went from ahead in army size to well behind. Zerg quickly replaced drone losses and soon broke into the protoss natural in return.

on Destination

PurpleWave went 2 gate zealots into expansion. Neither bot had much understanding of the situation. Steamhammer massed lings, an all-in play to smash the opponent. In practice it’s successful against most bots, but zerg ends up way behind in economy. Protoss can play defensively for a while and then win easily—that’s how Tyr protoss beats Steamhammer.

The game is not long or exciting. PurpleWave expanded in the face of the zerg swarm and did not have enough zealots. I include it to show how little bots understand strategy. In the picture, Steamhammer has half the workers of protoss. With any insight into the army-economy balance, you have to conclude that it is not a time for protoss to take a risk like expanding or moving out. The zealots again went fatalistic; as soon as they realized that they had lost, they stopped fighting and (unable to retreat far) were caught and died. You can also see that in the picture. Steamhammer has related weaknesses that are different but as severe.

PurpleWave might have had a chance if it retreated to the ramp and canceled the nexus. It was the best option, at least.

I expect that PurpleWave will fix its bugs before long and start winning again.

Next: More games, versus McRave and KillAll.

I wasn’t expecting this: Afreeca in Korea pitted 2 low-ranked players against 3 bots each, then Stork against 4 bots (10 games total). The bots are MJbot (which I don’t know anything about), ZZZKBot, and Tscmoo playing random (in a version with a very strange zerg build). Stork also played against CherryPi.

• TeamLiquid thread
• Korean cast (skip ahead to about 40:00 for the first game)
• English cast (missing the first and last games)

Stork made it look easy. If you’re that good, it is easy. It was a treat to see Stork’s superior decisions and strong micro.

Tomorrow: The promised Steamhammer vs. PurpleWave games.

When I first promised Steamhammer-Tscmoo games, Steamhammer had been winning most games against Tscmoo terran, despite dangerously aggressive terran play. Some of the games were good. Since then, Tscmoo has been updated, and now most of the Tscmoo bots (all except protoss) are ranked just above Steamhammer. Games have gone both ways, but I think Tscmoo has the edge overall.

a September game

In this game on Roadrunner Steamhammer played a 3 hatch lurker build that was a direct counter to Tscmoo’s fast academy. If zerg had played accurately, it would have been an easy win. As it was, zerg was unclear on the concept of defense and narrowly held by accidentally making just enough zerglings in a hardscrabble game. If Steamhammer had played a mutalisk opening, it would have lost, because the muta openings make fewer lings. Here Tscmoo’s last attack has broken through and the small terran force is frying drones—most of the drones in the picture died.

But lurkers were already out, and Steamhammer broke the attack with a hammer blow and then turned the hammer outward.

a recent game

Lately, Tscmoo terran has been playing sequences of tricky tech switches. Tscmoo played random on Destination in this game and got terran. It’s a 2 player map, and terran started with a barracks on 6 hidden in the corner of the zerg natural out of sight of the scouting drone, an early proxy that could be deadly. Luckily, Steamhammer tries to be ready for anything against a random player, and it opened with a safe overpool. Tscmoo in turn scouted Steamhammer’s safe opening and opted not to train marines right away (they would have died uselessly), but to move on to the next tech.

Early zerglings still did not spot the barracks. Tscmoo made marines in time for Steamhammer’s expansion; it may be a coincidence, but maybe Tscmoo is smart enough to know the timing. In any case, as you can see from the unit counts, zerg was more than prepared.

Most of Steamhammer’s lings went to the terran main, as you can see in the minimap above. Tscmoo has strong worker defense, and the fight was not entirely one-sided. And of course Tscmoo had been preparing its next tech, vultures. When they were done, the vultures chased the lings out. Steamhammer knew what was coming, though, and put down a sunken in its main for safety, and one in the natural a little later when the natural finished. The vultures also did not achieve much.

Meanwhile, Tscmoo started a starport, the next tech switch. Steamhammer saw that too and put down a hydra den while trying to catch up in workers; despite killing a few SCVs, zerg was behind because it had made too many combat units. But instead of putting on wraith pressure, Tscmoo made an extreme move while waiting for wraith cloak research to finish: It added a tank (without siege) and pulled almost all its SCVs across the map for an all-in attack.

Steamhammer knew how to defend this one. Zerg made an emergency switch to mass lings with a few hydras, and with the help of the sunken the attack was beaten back with heavy losses. Zerg went from behind to ahead, plus Steamhammer started a spire and was able to safely return to droning up. Zerg had wasted money on lurker research, but it no longer mattered.

Tscmoo finally pulled the wraith switch, but the long delay meant that Steamhammer was again ready. The first wraith was able to kill a couple drones before scourge hatched. The wraith instantly cloaked when it saw the danger, but cloak is no use when you have chosen to fly right next to an overlord.

Steamhammer realized, more slowly than it should have, that mutas were the right choice, and brought pressure back to the terran. Tscmoo switched again, to valkyries for air defense, but zerg scourged most of them and terran could not hold the line long enough to build a stable force. (If it had, Steamhammer was still ahead and I think it would have switched to hydras and won anyway. It knows how.) Here scourge are intercepting the first valkyrie—by coincidence, the scourge were waiting by the starport (someday I’ll add code to do that on purpose).

I think Tscmoo showed greater ability, but it took big risks which did not pay off in this game. The SCV pull in particular was not a smart plan. Even so, you can see how easily zerg could have made a mistake and lost; Tscmoo earned its high place in the ranking.

Here’s a human game with a similar sequence of terran tricks: July vs Firebathero from 21 September, on the map Hitchhiker. Firebathero’s sequence of bunker to vultures to wraiths is 100% standard. July was ready and had some zerg tricks in response. Even if you don’t have much Starcraft expertise, it should be easy to see that this game is on a way higher level than the bot game.

I watched some CherryPi games to see how it plays.

versus terran

CherryPi scored 92% against the 4 terrans. How did that happen?

Well, only 2 of the terrans are strong by CherryPi’s standard, and it pre-learned openings against both of them. Against #3 Iron, CherryPi played a mass zergling opening. In games where Iron did not wall, game over. What made it work is that, if Iron did build a wall, CherryPi understood when the wall was open or closed. That’s good cleverness. The zerglings formed a concave so they themselves were safe from the defenders behind the wall and nothing of Iron’s could sneak through, then when the barracks lifted to open the wall, rushed in and rampaged. Against #12 LetaBot, CherryPi played the same zergling opening and won by sheer persistence in attacking.

Both Iron and LetaBot could have won with little risk by playing more cautiously.

Against the weaker terrans, #16 IceBot and #25 HannesBredberg, CherryPi’s learning quickly found winning builds. Against IceBot it settled on a slow-moving mutalisk build with too many hatcheries, powering drones while IceBot delayed moving out. It’s the only case I found where CherryPi tries to win eventually instead of quickly. The games are consistent wins but are not impressive. Against HannesBredberg it was the mass lings again.

the learning sequence

Except against the 5 opponents for which it pre-learned openings, CherryPi opened the first game versus each opponent with 4 pool. It succeeded against refreshingly few of them. If that didn’t work, it tried another opening, and another, and so on. Most of the openings are of the low econ “I’ll just run you over in 6 minutes” kind.

CherryPi apparently tries all its openings without worrying whether they are appropriate to the matchup. It tried a lurker opening in this game versus Microwave. It made no sense to me, but maybe some zerg bots are vulnerable to lurkers.

CherryPi’s favorite unit is the zergling. Occasionally mutalisks or lurkers do something essential, but most of the time, early game or late, it wants to win with lings.

the Steamhammer family

#10 Steamhammer upset #6 CherryPi 72-32. The random openings worked as intended and baffled CherryPi’s learning. CherryPi has openings that could have won the majority of games (it won 7 of the first 10), but it could not find them (it won 3 of the last 10). It could not hear the learning signal over the noise.

Steamhammer forks cpac, Microwave, and Arrakhammer also had plus scores versus CherryPi. I doubt they were all for the same reason.

Next: Cpac.

The best-of-5 match Larva (Z) versus Rain (P) was played today. I think it is one of the best and most intense series in the post-Kespa era. Recommended.

Steamhammer and Microwave are both rated close to 2200 at the moment, putting them in the top ranks on SSCAIT. There is a big pileup at that skill level; only Krasi0 and Iron are significantly stronger. And yet a few days ago, Steamhammer and Microwave struggled against each other in a game with so much nonsense play that I was raging at them the whole time, sitting on the sofa with a laptop and shouting “Why are you doing that? DON’T DO THAT! Aargh!” Facepalm. There is so far to go.

It had better be true that you learn the most from mistakes, because there are a lot of painful mistakes here that are hard to look at.

The game is Steamhammer vs Microwave on Icarus. Steamhammer opened overlord, then hatchery, spawning pool, and gas all on 9/17. Microwave opened spawning pool on 9 and gas. Steamhammer’s worker defense is poor and the 9 pool will win if Microwave sends its zerglings immediately in the right direction. Microwave scouted with a drone and found Steamhammer’s base on the second try, which was too late. But Steamhammer's zerglings were distracted by the scouting drone, and Steamhammer did well to survive with 2 drones lost. Microwave could have won on the spot if it had scouted with an overlord, or if it had inferred Steamhammer’s base location when it saw Steamhammer’s overlord.

Steamhammer continued to chase the scouting drone. Urgh. The misbehavior is still there because I haven’t found an easy way to prevent it that doesn’t cause other bad behaviors—if it ignores the scout, that’s bad too. My plan to fix it requires time and care, so I’m putting it off for now. Anyway, moving the zerglings out of position offered opportunities to Microwave to stab into the mineral line, but Microwave played overcautiously and did not. Aggressive play would be to rush all zerglings in to wreak havoc, then try to escape when Steamhammer reacts, so that you don’t lose to the counter. Safe play would be to detach 2 to 4 zerglings to try to catch a drone, while keeping the others back for defense; if the raiders are surrounded and lost it is no terrible setback, and if they kill a drone that is an edge.

Steamhammer finally killed the scout and started to realize the advantages of its build. With 2 hatcheries from the start, it was far ahead in zerglings, and Microwave was forced into static defense. Microwave added 2 sunkens in its main... and expanded, so then it added 2 more sunkens at its natural. 4 sunkens are a fatal expense, and Steamhammer was miles ahead. In the picture, Steamhammer has so many more zerglings that it should have attacked immediately.

There are a lot more mistakes in the rest of the game, but the story is getting tiresome. Steamhammer refused chance after chance to widen its lead or win outright. It held back when it should have attacked. It built an ultralisk cavern and researched the expensive ultra upgrades, then did not build a single ultralisk until they lost their value. It made guardians and devourers and used them wastefully (partly because it hit a bug which assigned units to the wrong squads). It became so lax in applying pressure that Microwave caught up in economy. You can watch the end of the game yourself, if you can stomach it.

It was much smoother than past Steamhammer games that I have blogged as disastrously bad. The bot is slowly getting more solid.

Working on scouting reminded me: There is a trick that terran can play to mightily confuse the opponent’s early scout. At the start of the game, make SCVs as usual, then when it nears time for the opponent’s scout to approach, lift off the command center and move it out of sight. Of course you have to build any supply depots or other buildings out of sight too, or away from your base (you could proxy 8 rax, or build your first depot in an empty main base). It can only conceivably be a good idea if there is another base close by to land the command center at, so the trick should be saved for maps like Electric Circuit which have an inside “backdoor” base near the main.

The opponent will scout every main base and see you at none of them.

This trick has been used in one pro game to my knowledge, Boxer versus Yellow from 2003, where the CC move was meant to keep the proxy barracks unknown; a base without barracks would have given it away. If it were a good trick it would have been used since then. It’s objectively bad, and human players who see that all bases are empty are able to figure out what happened. But in bot play, you might fool your opponent into doing something nonsensical or even cause it to crash.

When UAlbertaBot’s scout is looking for the enemy base and finds an enemy building in a starting base region, is assumes that that marks the location of the enemy base. Steamhammer inherited the heuristic and still uses it. So a low-cost way to fool these bots is to build a supply depot or pylon next to the ramp of an empty main base before it is scouted. Zerg could build an extractor at the empty base, if the gas is toward the ramp. 50% of the time, the scouting worker will find the decoy building first and will not scout other bases. Nobody has tried this trick yet, as far as I have seen.

One of the themes of today’s SSCAIT broadcast by Nepeta is that too much static defense is bad for you. He repeatedly showed in ZvZ that the side which made too many sunkens tended to fall behind. Static defense can’t go attack; it costs resources and it offers initiative to the opponent. In a well-played game, static defense has to pay for itself with a countervailing advantage: You have to use the temporary safety it brings to get ahead in economy, as in a protoss forge-expand opening or as Killerbot by Marian Devecka tries to do, or to get ahead in tech, as when in ZvZ you make a sunken to tide yourself over until your spire finishes.

But there is a reason that so many bots play turtle strategies. Turtling is strong against bots which do not adapt, which is most of them. For Steamhammer, I added 1 base and 2 base turtle openings which crush Wuli, an opponent that Steamhammer otherwise struggles against. Wuli does not adapt.

Steamhammer does adapt to static defense and pulls ahead of opponents that turtle too much. When the opponent makes static defense, you have 3 broad strategic choices. They are the same 3 choices you always have, but the opponent has offered you initiative so any of them might give you an advantage. 1. You can pull ahead in army and bust the defenses. Example: Hydralisk bust versus protoss forge expand. It can win outright, but it is risky. 2. Use the opponent’s passivity to pull ahead in tech. If you made a sunken, other things being equal I can safely skip a few lings and get a faster spire. 3. Or similarly, pull ahead in economy. If you made sunkens, I can make drones.

Steamhammer primarily adapts by making drones. A protoss or terran bot might expand sooner instead, so it can build workers faster. But whatever the choice, you want to adapt so that you don’t end up crushed like Wuli.

The game Steamhammer vs KillAll (correcting the unfortunate typo in the bot’s name) is an example. KillAll opened 9 pool with extractor trick to get 10 drones, and Steamhammer unluckily chose 5 pool. It is a build order win for KillAll—if both sides play well, the 9 pool wins with little risk.

But instead of making a second hatchery to win with mass lings, or getting quick gas to win with mutalisks, KillAll turtled. It threw away its advantage.

You may want 1 sunken, because the 5 pooler starts making lings sooner and can be a little ahead. 5 sunkens are 4 too many and put KillAll behind despite its stronger opening. They are not well placed; they don’t protect either the approaches or the mineral line.

If I had been playing, I would have made a moderate number of drones, teched fast, expanded once for a second gas to guarantee that I would stay ahead, and aimed to win with mutalisks. Steamhammer made many drones and teched slowly (fast enough not to fall behind), spending the extra income on zerglings. It went up to 5 hatcheries to produce a biblical flood of zerglings. The picture shows 3 of the 5 hatcheries; the other 2 are in the natural. Steamhammer is slightly ahead in economy and tech and way ahead in army and production capacity. Steamhammer can only lose if it blunders.

The zerglings were so many that they cracked the turtle shell and overran KillAll. GG. KillAll lost drones right off because the sunkens were misplaced, but it took only a fraction of the zerglings to finish off the sunkens. Steamhammer had a completed spire but did not need any mutalisks (see how many purple zerglings are already en route).

Steamhammer’s reaction to static defense is effective. You can beat it with a turtle strategy, but only by exploiting weaknesses. The reaction to static defense is not a weakness.

Igor Dimitrijevic has uploaded a new version of Stone, a version which attacks buildings instead of workers. I guess it’s because worker defense has been steadily improving, but many bots still don’t react when a building comes under attack.

Steamhammer doesn’t react to attacks on buildings. Even so, its usual anti-rush opening defended successfully in this game. Buildings have a lot of hit points, so the spawning pool finished before it was destroyed. In the picture, the spawning pool is about to die before any zerglings are spawned, but the sunken colony is already morphing.

The sunken protected the hatchery completely, so there was little risk. Steamhammer replaced the spawning pool in the same position, which was not safe because the sunken protection extended to only one side of the pool. Stone did not seem to understand the range of the sunken, and half the SCVs sent to attack the pool were killed while standing just inside the danger zone. Steamhammer actually won the game more easily than against the older Stone version, because Stone threw away so many SCVs. Stone did point out weaknesses. Steamhammer should defend buildings which are in danger of being lost, and it needs better building placement.

This game versus Skynet by Andrew Smith was fun. Skynet, ahead of its time as usual, does react when buildings are attacked, and pulled many probes to defend. Skynet was unworried by the skirmishes and calmly continued with its build: Late gateway, gas, cyber core... all before the first combat unit.

My impression is that the change to Stone has left it weaker overall. Buildings are too hard to kill. Still, it does easily wipe out some opponents, and every change is a new challenge.